Methods for producing uniform large-grained and grain boundary location manipulated polycrystalline thin film semiconductors using sequential lateral solidification

ABSTRACT

Methods for processing an amorphous silicon thin film sample into a polycrystalline silicon thin film are disclosed. In one preferred arrangement, a method includes the steps of generating a sequence of excimer laser pulses, controllably modulating each excimer laser pulse in the sequence to a predetermined fluence, homoginizing each modulated laser pulse in the sequence in a predetermined plane, masking portions of each homoginized fluence controlled laser pulse in the sequence with a two dimensional pattern of slits to generate a sequence of fluence controlled pulses of line patterned beamlets, each slit in the pattern of slits being sufficiently narrow to prevent inducement of significant nucleation in region of a silicon thin film sample irradiated by a beamlet corresponding to the slit, irradiating an amorphous silicon thin film sample with the sequence of fluence controlled slit patterned beamlets to effect melting of portions thereof corresponding to each fluence controlled patterned beamlet pulse in the sequence of pulses of patterned beamlets, and controllably sequentially translating a relative position of the sample with respect to each of the fluence controlled pulse of slit patterned beamlets to thereby process the amorphous silicon thin film sample into a single or polycrystalline silicon thin film.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 09/390,535 filed on Sep. 3, 1999 (the “Parent Application”), whichhas issued as U.S. Pat. No. 6,555,449 and is a continuation-in-part ofapplication No. PCT/US96/07730, filed on May 28, 1996, and applicationSer. No. 09/200,533, filed on Nov. 27, 1998, which has issued as U.S.Pat. No. 6,322,625 the entire disclosures of which are incorporatedherein by reference. Thus, the present applications claims priority fromthe Parent Application under 35 U.S.C. § 120.

NOTICE OF GOVERNMENT RIGHTS

The U.S. Government has certain rights in this invention pursuant to theterms of the Defense Advanced Research Project Agency award numberN66001-98-1-8913.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to techniques for semiconductorprocessing, and more particularly to semiconductor processing which maybe performed at low temperatures.

II. Description of the Related Art

In the field of semiconductor processing, there have been severalattempts to use lasers to convert thin amorphous silicon films intopolycrystalline films. For example, in James Im et al., “Crystalline SiFilms for Integrated Active-Matrix Liquid-Crystal Displays,” 11 MRSBullitin 39 (1996), an overview of conventional excimer laser annealingtechnology is presented. In such a system, an excimer laser beam isshaped into a long beam which is typically up to 30 cm long and 500micrometers or greater in width. The shaped beam is scanned over asample of amorphous silicon to facilitate melting thereof and theformation of polycrystalline silicon upon resolidification of thesample.

The use of conventional excimer laser annealing technology to generatepolycrystalline silicon is problematic for several reasons. First, thepolycrystalline silicon generated in the process is typically smallgrained, of a random microstructure, and having a nonuniform grainsizes, therefore resulting in poor and nonuniform devices andaccordingly, low manufacturing yield. Second, in order to obtainacceptable performance levels, the manufacturing throughput forproducing polycrystalline silicon must be kept low. Also, the processgenerally requires a controlled atmosphere and preheating of theamorphous silicon sample, which leads to a reduction in throughputrates. Accordingly, there exists a need in the field to generate higherquality polycrystalline silicon at greater throughput rates. Therelikewise exists a need for manufacturing techniques which generatelarger and more uniformly microstructured polycrystalline silicon thinfilms to be used in the fabrication of higher quality devices, such asflat panel displays.

SUMMARY OF THE INVENTION

An object of the present invention is to provide techniques forproducing uniform large-grained and grain boundary location controlledpolycrystalline thin film semiconductors using the sequential lateralsolidification process.

A further object of the present invention is to form large-grained andgrain boundary location manipulated polycrystalline silicon oversubstantially the entire semiconductor sample.

Yet another object of the present invention is to provide techniques forthe fabrication of semiconductors devices useful for fabricatingdisplays and other products where the predominant orientation of thesemiconductor grain boundaries may be controllably aligned or misalignedwith respect to the current flow direction of the device.

In order to achieve these objectives as well as others that will becomeapparent with reference to the following specification, the presentinvention provides methods for processing an amorphous silicon thin filmsample into a polycrystalline silicon thin film are disclosed. In onepreferred arrangement, a method includes the steps of generating asequence of excimer laser pulses, controllably modulating each excimerlaser pulse in the sequence to a predetermined fluence, homoginizingeach modulated laser pulse in the sequence in a predetermined plane,masking portions of each homoginized fluence controlled laser pulse inthe sequence with a two dimensional pattern of slits to generate asequence of fluence controlled pulses of line patterned beamlets, eachslit in the pattern of slits being sufficiently narrow to preventinducement of significant nucleation in region of a silicon thin filmsample irradiated by a beamlet corresponding to the slit, irradiating anamorphous silicon thin film sample with the sequence of fluencecontrolled slit patterned beamlets to effect melting of portions thereofcorresponding to each fluence controlled patterned beamlet pulse in thesequence of pulses of patterned beamlets, and controllably sequentiallytranslating a relative position of the sample with respect to each ofthe fluence controlled pulse of slit patterned beamlets to therebyprocess the amorphous silicon thin film sample into a single orpolycrystalline silicon thin film.

In a preferred arrangement, the masking step includes masking portionsof each homoginized fluence controlled laser pulse in said sequence witha two dimensional pattern of substantially parallel straight slitsspaced a predetermined distance apart and linearly extending parallel toone direction of said plane of homoginization to generate a sequence offluence controlled pulses of slit patterned beamlets. Advantageously,the translating provides for controllably sequentially translating therelative position of the sample in a direction perpendicular to each ofthe fluence controlled pulse of slit patterned beamlets oversubstantially the predetermined slit spacing distance, to the to therebyprocess the amorphous silicon thin film sample into polycrystallinesilicon thin film having long grained, directionally controlledcrystals.

In an especially preferred arrangement, the masking step comprisesmasking portions of each homoginized fluence controlled laser pulse inthe sequence with a two dimensional pattern of substantially parallelstraight slits of a predetermined width, spaced a predetermined distancebeing less than the predetermined width apart, and linearly extendingparallel to one direction of the plane of homoginization to generate asequence of fluence controlled pulses of slit patterned beamlets. Inthis arrangement, translating step comprises translating by a distanceless than the predetermined width the relative position of the sample ina direction perpendicular to each of the fluence controlled pulse ofslit patterned beamlets, to the to thereby process the amorphous siliconthin film sample into polycrystalline silicon thin film having longgrained, directionally controlled crystals using just two laser pulses.In one exemplary embodiment, the predetermined width is approximately 4micrometers, the predetermined spacing distance is approximately 2micrometers, and the translating distance is approximately 3micrometers.

In an alternative preferred arrangement, the masking step comprisesmasking portions of each homoginized fluence controlled laser pulse inthe sequence with a two dimensional pattern of substantially parallelstraight slits spaced a predetermined distance apart and linearlyextending at substantially 45 degree angle with respect to one directionof the plane of homoginization to generate a sequence of fluencecontrolled pulses of slit patterned beamlets. In this arrangement, thetranslating step provides for controllably sequentially translating therelative position of the sample in a direction parallel to the onedirection of the plane of homoginization over substantially thepredetermined slit distance, to thereby process the amorphous siliconthin film sample into polycrystalline silicon thin film having longgrained, directionally controlled crystals that are disoriented withrespect to the XY axis of the thin silicon film.

In yet another preferred arrangement, the masking step comprises maskingportions of each homoginized fluence controlled laser pulse in thesequence with a two dimensional pattern of intersecting straight slits,a first group of straight slits being spaced a first predetermined apartand linearly extending at substantially 45 degree angle with respect toa first direction of the plane of homoginization, and a second group ofstraight slits being spaced a second predetermined distance apart andlinearly extending at substantially 45 degree angle with respect to asecond direction of the plane of homoginization and intersecting thefirst group at substantially a 90 degree angle, to generate a sequenceof fluence controlled pulses of slit patterned beamlets. Thecorresponding translating step provides for controllably sequentiallytranslating the relative position of the sample in a direction parallelto the first direction of the plane of homoginization over substantiallythe first predetermined slit spacing distance, to thereby process theamorphous silicon thin film sample into polycrystalline silicon thinfilm having large diamond shaped crystals.

In still another alternative arrangement, the masking step comprisesmasking portions of each homoginized fluence controlled laser pulse inthe sequence with a two dimensional pattern of sawtooth shaped slitsspaced a predetermined distance apart and extending generally parallelto one direction of the plane of homoginization to generate a sequenceof fluence controlled pulses of slit patterned beamlets. In thisarrangement, the translating step provides for controllably sequentiallytranslating the relative position of the sample in a directionperpendicular to each of the fluence controlled pulse of slit patternedbeamlets over substantially the predetermined slit spacing distance, tothe to thereby process the amorphous silicon thin film sample intopolycrystalline silicon thin film having large hexagonal crystals.

In a modified arrangement, an alternative technique for processing anamorphous silicon thin film sample into a polycrystalline silicon thinfilm using a polka-dot pattern is provided. Te technique includesgenerating a sequence of excimer laser pulses, homoginizing each laserpulse in the sequence in a predetermined plane, masking portions of eachhomoginized laser pulse in the sequence with a two dimensional patternof substantially opaque dots to generate a sequence of pulses of dotpatterned beamlets, irradiating an amorphous silicon thin film samplewith the sequence of dot patterned beamlets to effect melting ofportions thereof corresponding to each dot patterned beamlet pulse inthe sequence of pulses of patterned beamlets, and controllablysequentially translating the sample relative to each of the pulses ofdot patterned beamlets by alternating a translation direction in twoperpendicular axis and in a distance less than the super lateral growndistance for the sample, to thereby process the amorphous silicon thinfilm sample into a polycrystalline silicon thin film.

The accompanying drawings, which are incorporated and constitute part ofthis disclosure, illustrate a preferred embodiment of the invention andserve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of a system for performing the lateralsolidification process preferred to implement a preferred process of thepresent invention;

FIG. 2 a is an illustrative diagram showing a mask having a dashedpattern;

FIG. 2 b is an illustrative diagram of a crystallized silicon filmresulting from the use of the mask shown in FIG. 2 a in the system ofFIG. 1;

FIG. 3 a is an illustrative diagram showing a mask having a chevronpattern;

FIG. 3 b is an illustrative diagram of a crystallized silicon filmresulting from the use of the mask shown in FIG. 3 a in the system ofFIG. 1;

FIG. 4 a is an illustrative diagram showing a mask having a linepattern;

FIG. 4 b is an illustrative diagram of a crystallized silicon filmresulting from the use of the mask shown in FIG. 4 a in the system ofFIG. 1;

FIG. 5 a is an illustrative diagram showing irradiated areas of asilicon sample using a mask having a line pattern;

FIG. 5 b is an illustrative diagram showing irradiated areas of asilicon sample using a mask having a line pattern after initialirradiation and sample translation has occurred;

FIG. 5 c is an illustrative diagram showing a crystallized silicon filmafter a second irradiation has occurred;

FIG. 6 a is an illustrative diagram showing a mask having a diagonalline pattern;

FIG. 6 b is an illustrative diagram of a crystallized silicon filmresulting from the use of the mask shown in FIG. 6 a in the system ofFIG. 1;

FIG. 7 a is an illustrative diagram showing a mask having a sawtoothpattern;

FIG. 7 b is an illustrative diagram of a crystallized silicon filmresulting from the use of the mask shown in FIG. 7 a in the system ofFIG. 1;

FIG. 8 a is an illustrative diagram showing a mask having a crossingdiagonal line pattern;

FIG. 8 b is an illustrative diagram of a crystallized silicon filmresulting from the use of the mask shown in FIG. 8 a in the system ofFIG. 1;

FIG. 9 a is an illustrative diagram showing a mask having a polka-dotpattern;

FIG. 9 b is an instructive diagram illustrating mask translation usingthe mask of FIG. 9 a;

FIG. 9 c is an illustrative diagram of a crystallized silicon filmresulting from the use of the mask shown in FIG. 9 a in the system ofFIG. 1 using the mask translation scheme shown in FIG. 9 b;

FIG. 9 d is an illustrative diagram of an alternative crystallizedsilicon film resulting from the use of the mask shown in FIG. 9 a in thesystem of FIG. 1 using the mask translation scheme shown in FIG. 9 b;and

FIG. 10 is a flow diagram illustrating the steps implemented in thesystem of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides techniques for producing uniformlarge-grained and grain boundary location controlled polycrystallinethin film semiconductors using the sequential lateral solidificationprocess. In order to fully understand those techniques, the sequentiallateral solidification process must first be appreciated.

The sequential lateral solidification process is a technique forproducing large grained silicon structures through small-scaleunidirectional translation of a silicon sample in between sequentialpulses emitted by an excimer laser. As each pulse is absorbed by thesample, a small area of the sample is caused to melt completely andresolidify laterally into a crystal region produced by the precedingpulses of a pulse set.

A particularly advantageous sequential lateral solidification processand an apparatus to carry out that process are disclosed in ourco-pending patent application entitled “Systems and Methods usingSequential Lateral Solidification for Producing Single orPolycrystalline Silicon Thin Films at Low Temperatures,” filedconcurrently with the present application and assigned to the commonassignee, the disclosure of which is incorporated by reference herein.While the foregoing disclosure is made with reference to the particulartechniques described in our co-pending patent application, it should beunderstood that other sequential lateral solidification techniques couldreadily be adapted for use in the present invention.

With reference to FIG. 1, our co-pending patent application describes asa preferred embodiment a system including excimer laser 110, energydensity modulator 120 to rapidly change the energy density of laser beam111, beam attenuator and shutter 130, optics 140, 141, 142 and 143, beamhomogenizer 144, lens system 145, 146, 148, masking system 150, lenssystem 161, 162, 163, incident laser pulse 164, thin silicon film sample170, sample translation stage 180, granite block 190, support system191, 192, 193, 194, 195, 196, and managing computer 100 X and Ydirection translation of the silicon sample 170 may be effected byeither movement of a mask 210 within masking system 150 or by movementof the sample translation stage 180 under the direction of computer 100.

As described in further detail in our co-pending application, anamorphous silicon thin film sample is processed into a single orpolycrystalline silicon thin film by generating a plurality of excimerlaser pulses of a predetermined fluence, controllably modulating thefluence of the excimer laser pulses, homoginizing the modulated laserpulses in a predetermined plane, masking portions of the homoginizedmodulated laser pulses into patterned beamlets, irradiating an amorphoussilicon thin film sample with the patterned beamlets to effect meltingof portions thereof corresponding to the beamlets, and controllablytranslating the sample with respect to the patterned beamlets and withrespect to the controlled modulation to thereby process the amorphoussilicon thin film sample into a single or polycrystalline silicon thinfilm by sequential translation of the sample relative to the patternedbeamlets and irradiation of the sample by patterned beamlets of varyingfluence at corresponding sequential locations thereon. The followingembodiments of the present invention will now be described withreference to the foregoing processing technique.

Referring to FIGS. 2 a and b, a first embodiment of the presentinvention will now be described. FIG. 2 a illustrates a mask 210incorporating a pattern of slits 220. The mask 210 is preferablyfabricated from a quartz substrate, and includes either a metallic ordielectric coating which is etched by conventional techniques to form amask pattern, such as that shown in FIG. 2 a. Each slit 220 is of abreadth 230 which is chosen in accordance with the necessarydimensionality of the device that will be fabricated on the sample 170in the particular location that corresponds to the slit 220. Forexample, the slits 220 should be approximately 25 micrometers across tofabricate a 25 micrometer semiconductor device, or in the case of amulti-part device, a channel in a device, in sample 170. The width 240of the slit 220 is preferably between approximately two and fivemicrometers in order to be small enough to avoid nucleation in sample170 and large enough to maximize lateral crystal growth for each excimerpulse. It should be understood that although FIG. 2 a illustrates aregular pattern of slits 220, any pattern of slits could be utilized inaccordance with the microstructures desired to be fabricated on film170.

In accordance with the present invention, the sample 170 is translatedwith respect to the laser pulses 164, either by movement of maskingsystem 150 or sample translation stage 180, in order to grow crystalregions in the sample 170. When the sample 170 is translated in the Ydirection and mask 210 is used in masking system 150, a processed sample250 having crystallized regions 260 is produced, as shown in FIG. 2 b.The breadth 270 of each crystallized region will be approximately equalto the breadth 230 in the mask 210. The length 280 of each region willbe approximately equal to the distance of Y translation effected bymovement of the masking system 150 or translation stage 180, and as withthe breadth, should be chosen in accordance with the final devicecharacteristics. Each crystal region 260 will consist of polysiliconwith long and directionally controlled grains.

Referring next to FIGS. 3 a and b, a second embodiment of the presentinvention will now be described. FIG. 3 a illustrates a mask 310incorporating a pattern of chevrons 320. The breadth 320 of each chevronside will determine the size of the ultimate single crystal region to beformed in sample 170. When the sample 170 is translated in the Ydirection and mask 310 is used in masking system 150, a processed sample350 having crystallized regions 360 is produced, as shown in FIG. 3 b.Each crystal region 360 will consist of a diamond shaped single crystalregion 370 and two long grained, directionally controlledpolycrystalline silicon regions 380 in the tails of each chevron.

While the embodiments described with reference to FIGS. 2 and 3 areadvantageous to generate spatially separated devices on silicon sample170, at least some of the silicon sample 170 is not utilized in thefinal semiconductor. In order to facilitate a more flexibleconfiguration of devices that can be developed on the semiconductorsample 170, the following preferred embodiments will now be described.

Referring to FIGS. 4 a and b, a third embodiment of the presentinvention will now be described. FIG. 4 a illustrates a mask 410incorporating a pattern of slits 420. Each slit 410 should extend as faracross on the mask as the homogenized laser beam 149 incident on themask permits, and must have a width 440 that is sufficiently narrow toprevent any nucleation from taking place in the irradiated region ofsample 170. The width 440 will depend on a number of factors, includingthe energy density of the incident laser pulse, the duration of theincident laser pulse, the thickness of the silicon thin film sample, andthe temperature and conductivity of the silicon substrate. For example,the slit should not be more than 2 micrometers wide when a 500 Angstromfilm is to be irradiated at room temperature with a laser pulse of 30 nsand having an energy density that slightly exceeds the complete meltthreshold of the sample.

When the sample 170 is translated in the Y direction and mask 410 isused in masking system 150, a processed sample 450 having crystallizedregions 460 is produced, as shown in FIG. 4 b. Each crystal region 460will consist of long grained, directionally controlled crystals 470.Depending on the periodicity 421 of the masking slits 420 in sample 410,the length of the grains 470 will be longer or shorter. In order toprevent amorphous silicon regions from being left on sample 170, the Ytranslation distance must be smaller than the distance 421 between masklines, and it is preferred that the translation be at least one micronsmaller than this distance 421 to eliminate small crystals thatinevitably form at the initial stage of a directionally controlledpolycrystalline structure.

An especially preferred technique using a mask having a pattern of lineswill next be described. Using a mask as shown in FIG. 4 a where closelypacked mask lines 420 having a width 440 of 4 micrometers are eachspaced 2 micrometers apart, the sample 170 is irradiated with one laserpulse. As shown in FIG. 5 a, the laser pulse will melt regions 510, 511,512 on the sample, where each melt region is approximately 4 micrometerswide 520 and is spaced approximately 2 micrometers apart 521. This firstlaser pulse will induce the formation of crystal growth in theirradiated regions 510, 511, 512, starting from the melt boundaries 530and proceeding into the melt region, so that polycrystalline silicon 540forms in the irradiated regions, as shown in FIG. 5 b.

In order to eliminate the numerous small initial crystals 541 that format the melt boundaries 530, the sample 170 is translated threemicrometers in the Y direction and again irradiated with a singleexcimer laser pulse. The second irradiation regions 551, 552, 553 causethe remaining amorphous silicon 542 and initial crystal regions 543 ofthe polycrystalline silicon 540 to melt, while leaving the centralsection 545 of the polycrystalline silicon to remain. As shown in FIG. 5c, the crystal structure which forms the central section 545 outwardlygrows upon solidification of melted regions 542, 542, so that adirectionally controlled long grained polycrystalline silicon device isformed on sample 170.

Referring to FIGS. 6 a and b, a fourth embodiment of the presentinvention will now be described. FIG. 6 a illustrates a mask 610incorporating a pattern of diagonal lines 620. When the sample 170 istranslated in the Y direction and mask 610 is used in masking system150, a processed sample 650 having crystallized regions 660 is produced,as shown in FIG. 6 b. Each crystal region 660 will consist of longgrained, directionally controlled crystals 670.

As with the embodiment described above with respect to FIGS. 4 a and b,the translation distance will depend on the desired crystal length.Also, the process described with reference to FIGS. 5 a-c could readilybe employed using a mask as shown in FIG. 6 a, having 4 micrometer widelines 620 that are each spaced apart by 2 micrometers. This embodimentis especially advantageous in the fabrication of displays or otherdevices that are oriented with respect to an XY axis, as thepolycrystalline structure is not orthogonal to that axis andaccordingly, the device performance will be independent of the X or Ycoordinates.

Referring next to FIGS. 7 a and b, a fifth embodiment of the presentinvention will now be described. FIG. 7 a illustrates a mask 710incorporating offset sawtooth wave patterns 720, 721. When the sample170 is translated in the Y direction and mask 710 is used in maskingsystem 150, a processed sample 750 having crystallized regions 760 isproduced, as shown in FIG. 7 b. Each crystal region 760 will consist ofa row of hexagonal-rectangular crystals 770. If the translation distanceis slightly greater than the periodicity of the sawtooth pattern, thecrystals will be hexagons. This embodiment is beneficial in thegeneration of larger silicon grains and may increase device performance.

Referring next to FIGS. 8 a and b, a sixth embodiment of the presentinvention will now be described. FIG. 8 a illustrates a mask 810incorporating a diagonal cross pattern 821, 822. When the sample 170 istranslated in the Y direction and mask 810 is used in masking system150, a processed sample 850 having crystallized regions 860 is produced,as shown in FIG. 8 b. Each crystal region 860 will consist of a row ofdiamond shaped crystals 870. If the translation distance is slightlygreater than the periodicity of the pattern, the crystals will besquares. This embodiment is also beneficial in the generation of largersilicon grains and may increase device performance.

Referring next to FIGS. 9 a-d, a seventh embodiment of the presentinvention will now be described. FIG. 9 a illustrates a mask 910incorporating a polka-dot pattern 920. The polka-dot mask 910 is aninverted mask, where the polka-dots 920 correspond to masked regions andthe remainder of the mask 921 is transparent. In order to fabricatelarge silicon crystals, the polka-dot pattern may be sequentiallytranslated about the points on the sample 170 where such crystals aredesired. For example, as shown in FIG. 9 b, the polka-dot mask may betranslated 931 a short distance in the positive Y direction after afirst laser pulse, a short distance in the positive X direction 932after a second laser pulse, and a short distance in the negative Ydirection 933 after a third laser pulse to induce the formation of largecrystals. If the separation distance between polka-dots is greater thantwo times the lateral growth distance, a crystalline structure 950 wherecrystals 960 separated by small grained polycrystalline silicon regions961 is generated, as shown in FIG. 9 c. If the separation distance isless or equal to two times the lateral growth distance so as to avoidnucleation, a crystalline structure 970 where crystals 980 aregenerated, as shown in FIG. 9 d.

Referring next to FIG. 10, the steps executed by computer 100 to controlthe crystal growth process implemented with respect to FIG. 9 will bedescribed. FIG. 10 is a flow diagram illustrating the basic stepsimplemented in the system of FIG. 1. The various electronics of thesystem shown in FIG. 1 are initialized 1000 by the computer to initiatethe process. A thin silicon film sample is then loaded onto the sampletranslation stage 1005. It should be noted that such loading may beeither manual or robotically implemented under the control of computer100. Next, the sample translation stage is moved into an initialposition 1015, which may include an alignment with respect to referencefeatures on the sample. The various optical components of the system arefocused 1020 if necessary. The laser is then stabilized 1025 to adesired energy level and reputation rate, as needed to fully melt thesilicon sample in accordance with the particular processing to becarried out. If necessary, the attenuation of the laser pulses is finelyadjusted 1030.

Next, the shutter is opened 1035 to expose the sample to a single pulseof irradiation and accordingly, to commence the sequential lateralsolidification process. The sample is translated in the X or Ydirections 1040 in an amount less than the super lateral grown distance.The shutter is again opened 1045 to expose the sample to a single pulseof irradiation, and the sample is again translated in the X or Ydirections 1050 in an amount less than the super lateral growthdistance. Of course, if the sample was moved in the X direction in step1040, the sample should be moved in the Y direction in Step 1050 inorder to create a polka-dot. The sample is then irradiated with a thirdlaser pulse 1055. The process of sample translation and irradiation1050, 1055 may be repeated 1060 to grow the polka-dot region with fouror more laser pulses.

Next, if other areas on the sample have been designated forcrystallization, the sample is repositioned 1065, 1066 and thecrystallization process is repeated on the new area. If no further areashave been designated for crystallization, the laser is shut off 1070,the hardware is shut down 1075, and the process is completed 1080. Ofcourse, if processing of additional samples is desired or if the presentinvention is utilized for batch processing, steps 1005, 1010, and1035-1065 can be repeated on each sample.

The foregoing merely illustrates the principles of the invention.Various modifications and alterations to the described embodiments willbe apparent to those skilled in the art in view of the teachings herein.For example, the thin silicon film sample 170 could be replaced by asample having pre-patterned islands of silicon film. Also, the linepattern mask could be used to grow polycrystalline silicon using twolaser pulses as explained with reference to FIGS. 5 a-c, then rotated by90 degrees and used again in the same process to generate an array ofsquare shaped single crystal silicon. It will thus be appreciated thatthose skilled in the art will be able to devise numerous systems andmethods which, although not explicitly shown or described herein, embodythe principles of the invention and are thus within the spirit and scopeof the invention.

1. A method for processing a silicon thin film into a polycrystallinesilicon thin film, comprising the steps of: (a) generating a sequence ofexcimer laser pulses, each having a substantially predetermined size;(b) masking a laser pulse in the sequence with a mask having one or moreslits having a predetermined width to generate one or more first laserbeamlets corresponding to the laser pulse, such that each beamlet has ashape defined by a length corresponding to the predetermined laser pulsesize and a width corresponding to the slit width; (c) irradiating asilicon thin film with the one or more first laser beamlets to effectmelting of a first portion of the thin film corresponding to the shapeof the one or more laser beamlets; (d) translating at least one of thethin film and the excimer laser pulses relative to each other so thatone or more laser beamlets corresponding to a second laser pulse isincident on a second location of the thin film; and (e) after step (d),irradiating a second portion of the thin film with the one or moresecond laser beamlets corresponding to the second pulse to effectmelting of the second portion at the second film location, wherein thesecond portion partially overlaps the first portion,  wherein each ofthe irradiated portions is melted through a thickness of the thin filmand a lateral growth is effectuated in each molten portion of the thinfilm.
 2. The method according to claim 1, wherein the second portionpartially overlaps less than one half of the first portion.
 3. Themethod according to claim 1, wherein the laser beamlet width issufficient to prevent inducement of significant nucleation in a portionof the thin film that is irradiated by the laser beamlet.
 4. The methodaccording to claim 3, wherein at least one of the thin film and theexcimer laser pulses is translated relative to one another by a distanceof about 3 micrometers.
 5. The method according to claim 1, wherein atleast one of the thin film and the excimer laser pulses is translatedfor a distance that is greater than the lateral growth and less than thelaser beamlet width.
 6. The method according to claim 1, wherein theslit extends as far across the mask as the laser pulse incident on themask permits.
 7. A system for processing a silicon thin film into apolycrystalline silicon thin film, comprising: (a) an excimer laser forgenerating a plurality of excimer laser pulses of a predeterminedfluence, (b) an energy density modulator, optically coupled to saidexcimer laser, for controllably modulating said fluence of said excimerlaser pulses emitted by said excimer laser; (c) a beam homogenizer,optically coupled to said energy density modulator, for homogenizingsaid modulated laser pulses in a predetermined plane, said homogenizedlaser pulses each having a substantially predetermined size; (d) a maskhaving one or more slits having a predetermined width, optically coupledto said beam homogenizer, for masking each said homogenized modulatedlaser pulse to generate one or more laser beamlets corresponding to eachhomogenized laser pulse, such that each beamlet has a shape defined by alength corresponding to the predetermined laser pulse size and a widthcorresponding to the slit width; (e) a sample stage, optically coupledto said mask and adapted for translation, for receiving the one or morelaser beamlets for each laser pulse to effect melting of a portion ofany silicon thin film placed thereon corresponding to the shape of saidlaser beamlet; and (f) a computer, coupled to said excimer laser andsaid energy density modulator, for controlling said controllable fluencemodulation of said excimer laser pulses and relative positions of saidsample stage and said mask, and for coordinating said excimer pulsegeneration and said fluence modulation with said relative positions ofsaid sample stage and said mask, to thereby process said silicon thinfilm into a polycrystalline silicon thin film by sequential translationof said sample stage relative to said mask and irradiation of said thinfilm by one or more laser beamlets for each laser pulse at correspondingsequential locations thereon.
 8. The system according to claim 7,wherein the mask is adapted for translation.
 9. The system according toclaim 7, wherein the system comprises instructions executable by acomputer for: (g) irradiating a silicon thin film with the laser beamletto effect melting of a first portion of the thin film corresponding tothe shape of the predefined slit pattern in the mask; and (h) based ondimensions of the mask, translating at least one of the thin film andthe excimer laser pulses relative to the other one of the thin film andthe excimer laser pulse so as to reach a second location.
 10. A systemfor processing a silicon thin film into a polycrystalline silicon thinfilm, comprising: (a) a pulsed excimer laser for generating a pluralityof excimer laser pulses; each having a substantially predetermined size;(b) a mask having one or more slits having a predetermined width,optically coupled to said pulsed excimer laser pulses, for masking eachsaid laser pulse to generate one or more laser beamlets corresponding toeach laser pulse, such that each beamlet has a shape defined by a lengthcorresponding to the predetermined laser pulse size and a widthcorresponding to the slit width; (c) a sample stage, optically coupledto said mask and adapted for translation, for receiving the one or morelaser beamlets for each laser pulse to effect melting of a portion ofany silicon thin film placed thereon corresponding to the shape of saidlaser beamlet; (d) a computer, coupled to said excimer laser and saidsample stage, for controlling said excimer laser pulses and relativepositions of said sample stage and said mask, and for coordinating saidexcimer pulse generation with said relative positions of said samplestage and said mask; and (e) instructions on a computer readable mediumto thereby process said silicon thin film into a polycrystalline siliconthin film by sequential translation of said sample stage relative tosaid mask and irradiation of said thin film by one or more laserbeamlets for each laser pulse at corresponding sequential locationsthereon, wherein each of the irradiated portions is melted through athickness of the thin film and a lateral growth is effectuated in eachmolten portion of the thin film.
 11. The system according to claim 10,wherein the mask is adapted for translation.
 12. The system according toclaim 10, wherein the system comprises instructions executable by acomputer for: (g) irradiating a silicon thin film with the laser beamletto effect melting of a first portion of the thin film corresponding tothe shape of the predefined slit pattern in the mask; and (h) based ondimensions of the mask, translating at least one of the thin film andthe excimer laser pulses relative to the other one of the thin film andthe excimer laser pulse so as to reach a second location.